Afghanistan suffers more than 600 cases of terrorist or insurgency related violence a month, a fourfold increase from last year, according to a report.

The report, released on Sunday, came as 20 Taliban militants were killed in the latest fighting in eastern Afghanistan, an official said.

The Joint Coordination and Monitoring Board -- which consists of representatives from Afghanistan and the international community -- said in the report that Afghanistan was experiencing more than 600 security incidents a month as of the end of September, up from 300 a month at the end of March this year.

Last year, Afghanistan was recording about 130 incidents a month, it said, adding that the insurgency has killed more than 3,700 people this year.

"Confronting increased insurgent activity has diverted much of the government's attention and significant resources," the report said.

"It threatens to reverse some of the gains made in the recent past, with development activities being especially hard hit in several areas," it continued.

In eastern Afghanistan, meanwhile, General Murad Ali, the deputy Afghan army commander for Paktika Province, said 20 bodies were recovered from the fighting in Bermel district. In addition, he said, two trucks carrying Taliban fighters were destroyed by airstrikes or artillery fire, and officials estimated 40 fighters were killed in those strikes.

Four NATO soldiers and three Afghan soldiers were injured, he said, though a spokesman for NATO's International Security Assistance Force said he wasn't aware of any serious injuries among NATO troops.

Major Luke Knittig said the operations in Bermel, which borders Pakistan, were part of an ongoing Afghan-NATO mission to root out Taliban militants before winter settles in.

"We know we've engaged in successful operations in Bermel with a purpose, and we think those have had a very positive effect against insurgent activity there," Knittig said.

Knittig said Ali's estimate of 60 dead fighters "sounds about right to me," but he didn't have an independent estimate of the number killed.

Death tolls in remote areas of Afghanistan are almost impossible to verify and often vary widely.

Abdul Baqi Nuristani, the provincial police chief, said only 25 militants have been killed in Bermel district in the last couple days. He said three Afghan and three NATO soldiers were injured in what he called "a very big battle."

Ali said tribal elders took the bodies of eight Pakistani fighters back over the border to be buried.

Afghan officials have repeatedly accused Pakistan of not doing enough to prevent Pakistani or other foreign fighters from crossing the border to launch attacks. Pakistan says it does all it can, though border attacks have increased since a September agreement led the Pakistani military to pull out of its lawless tribal region.